The aim of this research investigation is to analyze four bodies of data dealing with elementary or secondary pupils either centering on, or containing information relevant to, the self-concept. The objective is to provide scientific information on the social determinants and consequences of children's self-concepts. The first is a sample of 5,024 high school students from ten high schools in New York State who completed questionnaires in l960. The second is a sample of l988 elementary and secondary school pupils from Baltimore City who were interviewed in l968. These two bodies of data were collected by the Principal Investigator, and focused on diverse aspects of the self-concept, including self-esteem, stability of the self-concept, anxiety, depression, self-consciousness, self-values, locus of self-knowledge, idealized and committed images, perceived self, and so on, as well as on certain social and psychological determinants and consequences of these aspects of the self-concept. In addition, two data sets containing longitudinal information on high school students have been acquired: (1) the National Longitudinal Survey, sponsored by the U.S. Office of Education; (2) the Youth in Transition project conducted by the Institute for Social Research of Michigan. Although a number of aspects of the self-concept will be considered, the immediate focus will be on self-concept change and development. In particular an attempt will be made to unravel the knotty cause-effect relationships between self-esteem and certain associated variables, such as parental attitudes and marks in school. Certain recent methodologca developments in the cross-lagged panel correlation technique offer particular promise for ferreting out such mutual effects. I also propose to look at the issue of change cross-sectionally in the Baltimore data, particularly with reference to developmental changes in the locus of self-knowledge.